Hundreds of men and boys from Middle Eastern countries were arrested by federal immigration officials in Southern California this week when they complied with orders to appear at INS offices for a special registration program.

The arrests drew thousands of people to demonstrate Wednesday in Los Angeles.

Immigration and Naturalization Service spokesmen refused Wednesday to say how many people the agency had detained, what the specific charges were or how many were still being held. But officials speaking anonymously said they would not dispute estimates by lawyers for detainees that the number across Southern California was 500 to 700. In Los Angeles, up to one-fourth of those who showed up to register were jailed, lawyers said.

The number of people arrested in this region appears to have been considerably larger than elsewhere in the country, perhaps because of the size of the Southland's Iranian population. Monday's registration deadline applied to males 16 and older from Iran, Iraq, Libya, Sudan and Syria. Men from 13 other nations, mostly in the Mideast and North Africa, are required to register next month.

Many of those arrested, according to their lawyers, had already applied for green cards and, in some instances, had interviews scheduled in the near future. Although they had overstayed their visas, attorneys argue, their clients had already taken steps to remedy the situation and were following the regulations closely.

"These are the people who've voluntarily gone" to the INS, said Mike S. Manesh of the Iranian American Lawyers Assn. "If they had anything to do with terrorism, they wouldn't have gone."

Immigration officials acknowledged Wednesday that many of those taken into custody this week have status-adjustment applications pending that have not yet been acted on.

"The vast majority of people who are coming forward to register are currently in legal immigration status," said local INS spokeswoman Virginia Kice. "The people we have taken into custody ... are people whose non-immigrant visas have expired."

The large number of Iranians among the detainees has angered many in the area's Iranian communities, who organized a demonstration Wednesday at the federal building in Westwood.

At the rally, which police officials estimated drew about 3,000 protesters at its peak, signs bore such sentiments as "What Next? Concentration Camps?" and "Detain Terrorists Not Innocent Immigrants."

The arrests have generated widespread publicity, mostly unfavorable, in the Middle East, said Khaled Dawoud, a correspondent for Al Ahram, one of Egypt's largest dailies. He questioned State Department official Charlotte Beers about the detentions Wednesday after a presentation she made at the National Press Club in Washington. Egyptians are not included in the registration requirement.

Beers, undersecretary of State for public diplomacy and public affairs, was presenting examples of a U.S. outreach campaign for the Middle East, which includes images of Muslims leading happy lives here. Dawoud asked how that image squared with the "humiliating" arrests in recent days.

"I don't think there is any question that the change in visa policy is going to be seen by some as difficult and, indeed — what was the word you used? — humiliating," Beers said. But, she added, President Bush has said repeatedly that he considers "his No. 1 ... job to be the protection of the American people."

Relatives and lawyers of those arrested locally challenge that rationale for the latest round of detentions.

One attorney, who said he saw a 16-year-old pulled from the arms of his crying mother, called it madness to believe that the registration requirements would catch terrorists.

"His mother is 6 1/2 months pregnant. They told the mother he is never going to come home — she is losing her mind," said attorney Soheila Jonoubi, who spent Wednesday amid the chaos of the downtown INS office attempting to determine the status of her clients.

Jonoubi said that the mother has permanent residence status and that her husband, the boy's stepfather, is a U.S. citizen. The teenager came to the country in July on a student visa and was on track to gain permanent residence, the lawyer said.

Many objected to the treatment of those who showed up for the registration. INS ads on local Persian radio stations and in other ethnic media led many to expect a routine procedure. Instead, the registration quickly became the subject of fear as word spread that large numbers of men were being arrested.

Lawyers reported crowded cells with some clients forced to rest standing up, some shackled and moved to other locations in the night, frigid conditions in jail cells — all for men with no known criminal histories.

Shawn Sedaghat, a Sherman Oaks attorney, said he and his partner, Michelle Taheripour, represent more than 40 people who voluntarily went to register and were detained.

Some, he said, were hosed down with cold water before finding places to sleep on the concrete floors of cells.

Lucas Guttentag, who heads the West Coast office of the American Civil Liberties Union's immigrant rights project, fears the wave of arrests is "a prelude to much more widespread arrests and deportations."

"The secrecy gives rise to obvious concerns about what the INS is doing and whether people's rights are being respected and whether the problems that arose in the aftermath of 9/11 are being repeated now," he said.

Many at Wednesday's protest said they took the day off work to join the rally, because they were shocked by the treatment.

"I came to this country over 40 years ago and got drafted in the Army, and I thought if I die it's for a good cause, defending freedom, democracy and the Constitution," said George Hassan, 65, from the San Fernando Valley.

"Oppressed people come here because of that democracy, that freedom, that Constitution. Now our president has apparently allowed the INS vigilantes to step outside the Constitution."

Ramona Ripston, executive director of the ACLU of Southern California, called the detentions doubly disturbing because "a lot of the Iranians are Jews who fled Iran because of persecution, and now they are undergoing similar persecution here.... This is just terrible."

Attorney Ban Al-Wardi, who saw 14 of her 20 clients arrested when she went with them to the registration, said that although everyone understands the need to protect the nation against terrorist attacks, the government's recent action went too far.

"All of our fundamental civil rights have been violated by these actions," she said. "I don't know how far this is going to go before people start speaking up. This is a very dangerous precedent we are setting. What's to stop Americans from being treated like this when they travel overseas?"

Times staff writers Greg Krikorian and Teresa Watanabe in Los Angeles and Johanna Neuman and Ricardo Alonso-Zaldivar in Washington contributed to this report.